怎么加个开关。。控制重复执行，弄了好几天要崩溃了。
就是运动后 p2 跟span复位，再次点击后又重新运动了

       window.onload = function(){
            var op = document.getElementById('p1');
            var op2 = document.getElementById('p2');
            var aSpan = op.getElementsByTagName('span');
            var len = 10;
            var num =0;
            var time = null;          
            
            for(var i=0;i0?Math.ceil(speed):Math.floor(speed);
            
            if(cur!=json[attr])
                bStop=false;
            
            if(attr=='opacity'){
                obj.style.filter='alpha(opacity:'+(cur+speed)+')';
                obj.style.opacity=(cur+speed)/100;
            }else{
                obj.style[attr]=cur+speed+'px';
            }
        }       
        if(bStop){
            clearInterval(obj.timer);                       
            if(fnEnd)fnEnd();
        }
    }, 30);
}